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1 // <coroutine> -*- C++ -*-
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2
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3 // Copyright (C) 2019-2020 Free Software Foundation, Inc.
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4 //
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5 // This file is part of the GNU ISO C++ Library. This library is free
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6 // software; you can redistribute it and/or modify it under the
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7 // terms of the GNU General Public License as published by the
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8 // Free Software Foundation; either version 3, or (at your option)
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9 // any later version.
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10
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11 // This library is distributed in the hope that it will be useful,
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12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
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13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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14 // GNU General Public License for more details.
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15
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16 // Under Section 7 of GPL version 3, you are granted additional
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17 // permissions described in the GCC Runtime Library Exception, version
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18 // 3.1, as published by the Free Software Foundation.
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19
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20 // You should have received a copy of the GNU General Public License and
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21 // a copy of the GCC Runtime Library Exception along with this program;
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22 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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23 // <http://www.gnu.org/licenses/>.
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24
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25 /** @file include/coroutine
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26 * This is a Standard C++ Library header.
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27 */
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28
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29 #ifndef _GLIBCXX_COROUTINE
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30 #define _GLIBCXX_COROUTINE 1
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31
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32 #pragma GCC system_header
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33
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34 // It is very likely that earlier versions would work, but they are untested.
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35 #if __cplusplus >= 201402L
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36
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37 #include <bits/c++config.h>
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38
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39 /**
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40 * @defgroup coroutines Coroutines
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41 *
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42 * Components for supporting coroutine implementations.
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43 */
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44
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45 #if __cplusplus > 201703L && __cpp_impl_three_way_comparison >= 201907L
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46 # include <compare>
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47 # define _COROUTINES_USE_SPACESHIP 1
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48 #else
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49 # include <bits/stl_function.h> // for std::less
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50 # define _COROUTINES_USE_SPACESHIP 0
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51 #endif
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52
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53 namespace std _GLIBCXX_VISIBILITY (default)
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54 {
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55 _GLIBCXX_BEGIN_NAMESPACE_VERSION
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56
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57 #if __cpp_coroutines
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58 inline namespace __n4835 {
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59
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60 // 17.12.2 coroutine traits
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61 /// [coroutine.traits]
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62 /// [coroutine.traits.primary]
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63 template <typename _Result, typename...>
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64 struct coroutine_traits
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65 {
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66 using promise_type = typename _Result::promise_type;
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67 };
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68
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69 // 17.12.3 Class template coroutine_handle
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70 /// [coroutine.handle]
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71 template <typename _Promise = void>
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72 struct coroutine_handle;
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73
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74 template <> struct
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75 coroutine_handle<void>
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76 {
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77 public:
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78 // 17.12.3.1, construct/reset
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79 constexpr coroutine_handle() noexcept : _M_fr_ptr(0) {}
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80
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81 constexpr coroutine_handle(std::nullptr_t __h) noexcept
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82 : _M_fr_ptr(__h)
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83 {}
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84
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85 coroutine_handle& operator=(std::nullptr_t) noexcept
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86 {
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87 _M_fr_ptr = nullptr;
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88 return *this;
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89 }
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90
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91 public:
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92 // 17.12.3.2, export/import
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93 constexpr void* address() const noexcept { return _M_fr_ptr; }
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94
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95 constexpr static coroutine_handle from_address(void* __a) noexcept
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96 {
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97 coroutine_handle __self;
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98 __self._M_fr_ptr = __a;
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99 return __self;
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100 }
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101
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102 public:
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103 // 17.12.3.3, observers
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104 constexpr explicit operator bool() const noexcept
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105 {
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106 return bool(_M_fr_ptr);
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107 }
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108
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109 bool done() const noexcept { return __builtin_coro_done(_M_fr_ptr); }
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110
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111 // 17.12.3.4, resumption
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112 void operator()() const { resume(); }
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113
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114 void resume() const { __builtin_coro_resume(_M_fr_ptr); }
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115
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116 void destroy() const { __builtin_coro_destroy(_M_fr_ptr); }
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117
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118 protected:
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119 void* _M_fr_ptr;
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120 };
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121
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122 // 17.12.3.6 Comparison operators
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123 /// [coroutine.handle.compare]
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124 constexpr bool operator==(coroutine_handle<> __a,
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125 coroutine_handle<> __b) noexcept
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126 {
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127 return __a.address() == __b.address();
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128 }
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129
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130 #if _COROUTINES_USE_SPACESHIP
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131 constexpr strong_ordering
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132 operator<=>(coroutine_handle<> __a, coroutine_handle<> __b) noexcept
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133 { return std::compare_three_way()(__a.address(), __b.address()); }
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134 #else
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135 // These are to enable operation with std=c++14,17.
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136 constexpr bool operator!=(coroutine_handle<> __a,
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137 coroutine_handle<> __b) noexcept
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138 {
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139 return !(__a == __b);
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140 }
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141
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142 constexpr bool operator<(coroutine_handle<> __a,
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143 coroutine_handle<> __b) noexcept
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144 {
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145 return less<void*>()(__a.address(), __b.address());
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146 }
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147
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148 constexpr bool operator>(coroutine_handle<> __a,
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149 coroutine_handle<> __b) noexcept
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150 {
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151 return __b < __a;
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152 }
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153
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154 constexpr bool operator<=(coroutine_handle<> __a,
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155 coroutine_handle<> __b) noexcept
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156 {
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157 return !(__a > __b);
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158 }
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159
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160 constexpr bool operator>=(coroutine_handle<> __a,
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161 coroutine_handle<> __b) noexcept
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162 {
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163 return !(__a < __b);
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164 }
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165 #endif
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166
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167 template <typename _Promise>
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168 struct coroutine_handle : coroutine_handle<>
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169 {
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170 // 17.12.3.1, construct/reset
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171 using coroutine_handle<>::coroutine_handle;
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172
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173 static coroutine_handle from_promise(_Promise& p)
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174 {
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175 coroutine_handle __self;
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176 __self._M_fr_ptr
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177 = __builtin_coro_promise((char*) &p, __alignof(_Promise), true);
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178 return __self;
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179 }
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180
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181 coroutine_handle& operator=(std::nullptr_t) noexcept
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182 {
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183 coroutine_handle<>::operator=(nullptr);
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184 return *this;
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185 }
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186
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187 // 17.12.3.2, export/import
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188 constexpr static coroutine_handle from_address(void* __a)
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189 {
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190 coroutine_handle __self;
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191 __self._M_fr_ptr = __a;
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192 return __self;
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193 }
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194
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195 // 17.12.3.5, promise accesss
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196 _Promise& promise() const
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197 {
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198 void* __t
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199 = __builtin_coro_promise (this->_M_fr_ptr, __alignof(_Promise), false);
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200 return *static_cast<_Promise*>(__t);
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201 }
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202 };
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203
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204 /// [coroutine.noop]
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205 struct noop_coroutine_promise
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206 {
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207 };
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208
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209 void __dummy_resume_destroy() __attribute__((__weak__));
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210 void __dummy_resume_destroy() {}
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211
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212 struct __noop_coro_frame
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213 {
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214 void (*__r)() = __dummy_resume_destroy;
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215 void (*__d)() = __dummy_resume_destroy;
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216 struct noop_coroutine_promise __p;
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217 } __noop_coro_fr __attribute__((__weak__));
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218
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219 // 17.12.4.1 Class noop_coroutine_promise
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220 /// [coroutine.promise.noop]
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221 template <>
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222 struct coroutine_handle<noop_coroutine_promise> : public coroutine_handle<>
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223 {
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224 using _Promise = noop_coroutine_promise;
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225
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226 public:
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227 // 17.12.4.2.1, observers
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228 constexpr explicit operator bool() const noexcept { return true; }
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229
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230 constexpr bool done() const noexcept { return false; }
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231
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232 // 17.12.4.2.2, resumption
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233 void operator()() const noexcept {}
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234
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235 void resume() const noexcept {}
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236
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237 void destroy() const noexcept {}
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238
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239 // 17.12.4.2.3, promise access
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240 _Promise& promise() const
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241 {
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242 return *static_cast<_Promise*>(
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243 __builtin_coro_promise(this->_M_fr_ptr, __alignof(_Promise), false));
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244 }
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245
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246 // 17.12.4.2.4, address
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247 private:
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248 friend coroutine_handle<noop_coroutine_promise> noop_coroutine() noexcept;
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249
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250 coroutine_handle() noexcept { this->_M_fr_ptr = (void*) &__noop_coro_fr; }
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251 };
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252
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253 using noop_coroutine_handle = coroutine_handle<noop_coroutine_promise>;
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254
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255 inline noop_coroutine_handle noop_coroutine() noexcept
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256 {
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257 return noop_coroutine_handle();
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258 }
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259
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260 // 17.12.5 Trivial awaitables
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261 /// [coroutine.trivial.awaitables]
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262 struct suspend_always
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263 {
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264 bool await_ready() { return false; }
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265
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266 void await_suspend(coroutine_handle<>) {}
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267
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268 void await_resume() {}
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269 };
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270
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271 struct suspend_never
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272 {
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273 bool await_ready() { return true; }
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274
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275 void await_suspend(coroutine_handle<>) {}
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276
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277 void await_resume() {}
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278 };
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279
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280 } // namespace __n4835
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281
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282 #else
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283 #error "the coroutine header requires -fcoroutines"
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284 #endif
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285
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286 _GLIBCXX_END_NAMESPACE_VERSION
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287 } // namespace std
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288
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289 #endif // C++14 (we are allowing use from at least this)
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290
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291 #endif // _GLIBCXX_COROUTINE
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